This invention relates to a cooling device in an electronic equipment, and more particularly to a system which is constituted by a cooling structure and an reliability of the electronic equipment.
Recently, the processing speed of electronic equipments has become much higher, and the amount of heat, generated from semiconductors, has much increased. Generally, in an air-cooled electronic equipment apparatus such as a computer, a cooling structure (hereinafter referred to as "fan-incorporating heatsink"), in which fins and a fan are combined together in a unitary manner, is mounted on an LSI package which is a high heat-generating semiconductor device, and the semiconductor, which generates a large amount of heat, is cooled in a concentrated manner by such heatsink. For a board on which IC chips, such as a memory chip, (which are relatively low heat-generating semiconductor devices), and the above LSI package are mounted in a mixed manner, it is customary to simultaneously cool the IC chips and the LSI package.
For example, there has been proposed a cooling method using a fan-incorporating heatsink (as disclosed in Japanese Patent Unexamined Publication No. 62-49700), in which a heatsink of the fan-incorporating heatsink is mounted, taking the rotation of a fan into consideration, thereby enhancing the cooling performance of the heatsink.
Japanese Patent Unexamined Publication No. 1-28896 discloses a prior art technique of simultaneously cooling semiconductors which are mounted on the same board, and generate different amounts of heat, and more specifically, this publication discloses a technique in which there is provided a duct having a fan for supplying cooling air (cooling wind) to the high heat-generating semiconductor, and there is provided a fan for supplying cooling air to other low heat-generating semiconductors and the high heat-generating semiconductor.
Another prior art technique of cooling an electronic equipment is disclosed in Japanese Utility Model Unexamined Publication No. 63-164294. In this prior art technique, the orientation of a heatsink is so determined that if a cooling fan of the fan-incorporating heatsink is subjected to failure, a natural convection can be easily produced.
In the fan-incorporating heatsink disclosed in Japanese Patent Unexamined Publication No. 62-49700, when the amount of generation of heat from a semiconductor becomes large, the heatsink itself is heated to a high temperature, so that the temperature of the cooling fan connected to the heatsink also becomes high. The lifetime of the cooling fan is proportional to the lifetime of a bearing constituting a rotating portion thereof, and therefore the lifetime of the cooling fan of the fan-incorporating heatsink is extremely shortened as compared with the case where the cooling fan is provided in spaced relation to the semiconductor device as in the prior art techniques disclosed in Japanese Patent Unexamined Publication No. 1-28896 and Japanese Utility Model Unexamined Publication No. 63-164294.
Therefore, there is an extremely high possibility that the cooling fan of the fan-incorporating heatsink is stopped (that is, fails to operate). However, in the above prior technique disclosed in Japanese Patent Unexamined Publication No. 62-49700, no consideration is given to the failure of the cooling fan, and if this occurs, the cooling air can not be secured, and the temperature of the semiconductor abruptly rises beyond an operable limit to lead to destruction of the semiconductor. This problem has not been taken into consideration. Further, it has not been taken into account that the cooling air discharged from the fins of the fan-incorporating heatsink is again sucked into the cooling fan of the fan-incorporating heatsink for returning of the high temperature exhaust.
The conventional construction, disclosed in Japanese Patent Unexamined Publication No. 1-28896, is provided with the plurality of fans, but when any of these fans is stopped, sufficient cooling air can not be secured as in the prior art technique disclosed in Japanese Patent Unexamined Publication No. 62-49700, and this problem has not been taken into consideration. Particularly, the cooling air supplied from the fan in order to cool the low heat-generating devices and the high heat-generating device in common is caused to flow parallel to the board having these heat-generating devices mounted thereon, and therefore when the cooling fan for cooling the high heat-generating semiconductor device is stopped, the duct provided for each high heat-generating semiconductor forms a barrier to the flow of the cooling air, so that the cooling air can not be sufficiently supplied to the downstream-side low heat-generating semiconductors, as a result, the temperature of the downstream-side IC chips extremely rises. This problem has not been taken into consideration.
In the prior art technique disclosed in Japanese Utility Model Unexamined Publication No. 63-164294. although the failure of the fan is taken into consideration, heat radiation is effected by a natural convection. Recently, semiconductor devices are mounted close to one another, that is, at a high density, and in this case, high-temperature air becomes stagnant, which has not been taken into consideration. When the amount of heat generated from the semiconductor devices increases, additional cooling means, such as a separate discharge fan, must be provided, but this has not been taken into consideration.
In the above prior art techniques, when the fan is stopped, the temperature of the semiconductor abruptly rises, and therefore in order to prevent the semiconductor device from being destroyed, the supply of electric power thereto is immediately stopped, thereby stopping the generation of heat from the semiconductor device. However, if the supply of the electric power is stopped without taking into consideration data stored in the semiconductor device, there is a possibility that not only data prepared by the user of the air-cooled electronic equipment apparatus but also basic data and software indispensable to the operation of the air-cooled electronic equipment apparatus are destroyed. Therefore, it is necessary to allow a sufficient time for protecting the above necessary data before the supply of the electric power is stopped when the temperature of the semiconductor rises to its operating limit. However, this has not been taken into consideration.
As described above, in the above prior art techniques including one in which the semiconductors generating different amounts of heat are mounted on the same board, no consideration has been given to the problem that the supply of the cooling air to the high heat-generating device becomes insufficient when the fan of the fan-incorporating heatsink is stopped.
Besides, no consideration has been given to the need for performing processings to protect the necessary data and software so as to secure the redundancy of the apparatus before the supply of the electric power to the semiconductor device is stopped in association with stoppage of the fan. Namely, no consideration has been given to the type of cooling structure suitable for protecting such data and also to the construction of a system necessary for protecting the data.